Apparatus having a material feed means for the vacuum treatment of molten metal



United States Patent APPARATUS HAVING A MATERIAL FEED MEANS FOR THE VACUUM TREATMENT OF MQLTEN METAL Walter Sieckman, Canonsburg, Robert J. Taylor, McKees Rocks, and Eberhard G. Schernpp, Glenshaw, Pa assignors, by mesne assignments, to Lectrornelt Corporation, Pittsburgh, Pin, a corporation of Delaware Filed Sept. 8, 1965. Ser. No. 485,798 12 Claims. (Cl. 265-34) ABSTRACT OF THE DISCLOSURE Mechanism including a vibratory feeder having an output the function of which depends on either amplitude or frequency of vibration, means to sense this amplitude or frequency of vibration to produce a signal, and means to compare this signal against a standard so that the amplitude or frequency of vibration can be varied responsive thereto for maintaining the output of material at some rate predetermined by the standard. The mechanism is connected to a vacuum chamber and operates to feed additives to molten metal therein as required.

This invention relates to a method and apparatus for the vacuum treatment of molten metal and, more particularly, to a method and apparatus for feeding alloying additions into molten metal during vacuum treatment.

Increasing quality demands on certain alloy steels requires the removal of oxygen, hydrogen, and sometimes carbon, preferably in an operation subsequent to the melting of such steels in an electric furnace. Because the concentration of these elements is pressure dependent, their removal can be accomplished expeditiously by vacuum treatment.

The type of vacuum degassing apparatus used to illustrate the preferred embodiment of the instant invention is one wherein a vacuum chamber is disposed above a ladle of molten metal and the two are arranged for relative movement toward and away from each other. A nozzle extends downwardly from the lower end of the vacuum chamber so that upon movement of the chamber and the ladle toward each other, the reduced pressure within the chamber draws molten metal through the nozzle whereupon degasification takes place due to the action f the vacuum therewithin. Upon relative movement of the chamber and the ladle away from each other, the molten metal in the chamber discharges through the nozzle to intermix with the remaining metal within the ladle. If desired, a new portion of the melt may be drawn into the chamber by again relatively moving the vessel and the ladle toward each other. This process is repeated until the desired degree of total degasification has been achieved.

During the degasification of certain alloys, it may become necessary to add certain alloying or refining compounds to the melt. For example, in the production of heavy forgings, ditficulties have been experienced due to oxide inclusions. Significant quantities of oxygen, however, can be removed rapidly only when it is in a gaseous form. Therefore, it is essential to degas the melt prior to the addition of elements, such as silicon, which have a high oxygen aflinity. When making such additions late in the degassing cycle, it is possible first to remove most of the oxygen in the form of a gaseous deoxidation product, such as carbon monoxide.

Due to the configuration of the degassing apparatus, additions can most conveniently be made through the vacuum chamber. The addition of additives during degasification also has the advantage of increased speed in that the intermixing of the melt, inherent in the above- 3,410,548 Patented Nov. 12, 1968 ice described degasification process, eliminates the necessity for an additional mixing procedure. However, because the hopper used to insert such additives into the vacuum chamber must be a part of the overall sealed system, no additional material can be placed into the hopper once the degassing operation has commenced. For this reason, charging of the hopper must be completed prior to the initiation of the degassing operation.

It will be appreciated, too, that in order to obtain the specified alloy grades, it is necessary that the unit weight of additives per ton of melt be held within close tolerances. This is complicated by the fact that it is extremely difficult to accurately predetermine the exact yield of any given melting furnace.

In order to achieve the desired chemical composition for a particular melt, it is necessary to add certain alloying elements based on samples of the melt itself. It will be appreciated, however, that chemical composition analysis based on samples taken from the electric furnace might be subject to error due to a stratification in the furnace. Also, any chemical adjustment to be made in the electric furnace would necessarily mean an extension of costly furnace time. In addition, during the tapping operation itself, chemical composition of the steel can also change due to the exposure of the tapping stream to the air, i.e. oxidation of certain alloys. It is, therefore, desirable to take a sample from the ladle during the early cycles of the vacuum treatment, i.e. after the ladle has been uniformly mixed. This sample is then representative for the chemical analysis of the steel and, provided the sample results are available to the operator within the time of degassing, accurate adjustment to achieve precise analysis can be made by using the vacuum hoppers on top of the degassing chamber during vacuum treatment.

It is an object of the invention to provide a hopper for charging the melt in a vacuum degassing chamber with additives during a degassing operation.

A further object of the invention is to provide means for adding alloying or refining compounds to the melt in a vacuum degassing chamber from a sealed hopper wherein the weight of the material added can be controlled after the hopper has been sealed so that the additive weight can be made to accurately correspond to the weight of the melt being treated.

Yet another object of the invention is to provide apparatus for feeding a predetermined quantity of material into a metal treating system without the need for mechanical or electrical weighing device's.

Another object of the invention is to provide a method of treating molten metal comprising the steps of uniformly mixing a quantity of molten metal, determining the weight and chemical composition thereof, vacuum treating the molten metal and adding material to the molten metal at a constant rate and for a period determined by the weight and chemical analysis thereof and during the vacuum treatment.

These and other objects and advantages of the instant invention will become more apparent from the detailed description thereof taken with the accompanying drawings, in which:

FIG. 1 is a side elevational view, partly in section, of vacuum degassing apparatus incorporating the instant invention;

FIG. 2 schematically illustrates the additive feeding mechanism employed with the vacuum apparatus illustrated in FIG. 1; and

FIGS. 3-6 are curves illustrating the operation of the feeding mechanism shown in FIG. 2.

Referring now to the drawings in greater detail, FIG. 1 shows vacuum degassing apparatus comprising a vacuum degassing vessel 10, a ladle 11 containing molten metal 12 and a lifting mechanism 14 for supporting the vessel and for lifting it vertically relative to the ladle 11.

The degassing vessel 10 includes a steel shell 15 which encloses and provides support for an inner refractory lining 16 which defines a vacuum chamber 17; A molten metal conducting pipe 18 is aflixed to the lower end of the vessel 10 and has a cylindrical bore 19 which communicates with the interior of the chamber 17. The chamber 17 is connected to a suitable evacuating apparatus (not shown) by a conduit 20 which is afiixed in a sealed relation to the shell 15 and adjacent an aperture 21 in the roof of the refractory lining 16.

The lifting mechanism 14 includes a platform 22 upon which the vessel 10 is mounted and a plurality of coordinated hydraulic rams 23 for moving the platform 22 and the vessel 10 vertically relative to the ladle 11. Control of the hydraulic rams 23 is effected by an operator stationed at a remote location. It will be appreciated by those skilled in the art that while the vessel 10 is shown to be vertically movable in the illustrated embodiment, the device operates equally as well if the vessel 10 is stationary and the ladle 11 is movable.

After the ladle 11 of molten metal 12, such as steel, has been positioned below the vessel 10, the latter is lowered until the pipe 18 extends a predetermined distance below the surface of the melt 12. The evacuating apparatus (not shown) is then actuated to produce a partial vacuum within the chamber 17. As a result of the difference between the pressure within the chamber 17 and atmospheric pressure acting on the surface of the melt 12, a portion of said melt, identified by the reference numeral 12', is forced upward through the bore 19 in the pipe 18 and into the chamber 17 where gases dissolved therein are drawn off by the operation of the partial vacuum. After this portion 12' of the melt 12 has been degassed for a predetermined length of time, the vessel 10 is raised, thereby causing the melt 12' to discharge back into the ladle 11.

The lower end of the pipe 18, however, remains below the surface of the melt 12 to maintain the partial vacuum within the chamber 17. As a result, the process may then be repeated by successively lowering and raising the vessel 10 until the desired degree of total degasification has been achieved. Because the degassed portion of the metal 12' has a greater density than the untreated portion of the metal in the ladle 11, the degassed metal 12 settles to the bottom of the ladle 11 upon discharging from the vessel 10 so that successive portions of the melt 12, which are drawn into the chamber 17 from the upper portion of the ladle, will be substantially untreated.

The hopper 25 for charging the chamber 17 with refining or alloying additives, is mounted atop the steel shell 15 in any suitable manner and includes a short pipe 26 integral with and passing through the steel shell 15. An opening 27 in the roof of the lining 16 and adjacent the lower end of the pipe 26 places the hopper 25 in communication with the interior of the vessel 10. An externally controlled valve 28 is operative to discharge the contents of hopper 25 into the chamber 17.

As will be pointed out in greater detail hereinbelow, a generally cylindrical, hollow, horizontally disposed steel housing 29 opens into the side of the hopper 25 and extends laterally therefrom for enclosing a vibratory feeder 30 and has an interconnected vertically disposed portion 29' for housing a storage bin 31.

Turning now to FIG. 2, the vibratory feeder 30 is shown to include a tray 34, a tray vibrating mechanism 35, an energizing circuit 36 for the vibrating mechanism 35, a feedback transducer 37 for sensing the amount of material being fed and a control mechanism 38 for adjusting the energization of the vibrating mechanism in accordance with the amount of material being fed.

The vibrating apparatus 35 includes a moving mass 40 which is supported by springs 41 and which carries the tray 34. An armature 43 of magnetic material is connected to the mass 35 and supports a horseshoe shaped permanent magnet 44 with its poles extending generally upwardly. A fixedly mounted three pole electromagnet 45 is disposed with its poles intermeshed with and spaced from those of the permanent magnet 44 and has a coil 47 wound about its central leg.

The coil 47 is connected to the energizing circuit 36 which includes an alternating current source 48 and a pair of silicon controlled rectifiers 49 and 50 whose anodes and cathodes are connected in parallel with each other and oriented in an opposite sense so that, depending on the firing angle of each of the controlled rectifiers 49 and 50, current will flow to the coil 47 during each half cycle of the source 48.

The control mechanism 38 performs the function of controlling the firing angles of the controlled rectifiers 49 and 5t and, in the illustrated embodiment, comprises a magnetic amplifier 51 having a pair of load windings 52 and 53, respectively, connected to the gate electrodes of controlled rectifiers 49 and 50. In addition, the magnetic amplifier 51 includes a control winding 54 connected to a constant voltage supply through an adjustable resistor 56 and a switch 57 which is controlled by a timer 58. In addition, the magnetic amplifier 51 includes a feedback winding coupled to the feedback transducer 37.

The feedback transducer 37 is a vibration amplitude measuring device comprising a permanent magnet 59 which is afiixed to the tray 34 and a stationary coil 60. The feedback winding 55 is connected to the coil 60 of feedback transducer 37 through a full wave rectifier 61 whose input terminals are connected across the winding 60 and whose output terminals are connected across a potentiometer 62. The feedback Winding 55 is connected in series with a second potentiometer 63 and the series combination is connected across the potentiometer 62 so that a unidirectional voltage will be applied to winding 55 which is functionally related to the amplitude of the vibrations of tray 34. A capacitor 64 is connected between the wipers of potentiometers 62 and 63 and cooperates with potentiometer 63 to reduce the AC ripple from the full wave rectifier 61.

It will be appreciated that in the absence of a voltage signal across the control winding 54, the core 65 of magnetic amplifier 51 will remain unsaturated as the source 48 alternates so that no current will flow in either of the load windings 52 or 53. As a result, there will be no gate current to either of the controlled rectifiers 49 or 50 so the flow of current to the coil 47 will be blocked and the tray vibrating mechanism 35 will be at rest. It will also be appreciated that when the control coil 54 is energized, at least One leg of core 65 will become saturated during each half cycle of the source 48.

The timer 68 is calibrated in pounds of material to be fed and is normally set after the amount of material to be fed has been determined. When the switch 57 is closed by the timer to energize the control winding 54, the material feeding operation commences.

Assume that during the first half cycle of alternating voltage from the source 48 after the switch 57 is closed, the flux in core 65 resulting from the voltage in control coil 54 will aid that resulting from the voltage across coil 52 and oppose that resulting from the voltage across coil 53. As a result the coil 52 leg of the core 65 will saturate during the first half cycle whereupon the current will flow in coil 52 to provide a signal to the gate of controlled rectifier 49 which then becomes conductive to provide a voltage impulse to the winding 47. This impulse will continue until the end of the first half cycle of the source 48 even though the flux in the winding 52 leg of the core 65 decreases out of the saturation region as the sinusoidal voltage wave decreases toward zero and the gate signal ceases. When the sinusoidal voltage wave reverses the flux resulting from the voltage across control coil 54 will aid that in load Winding 53 and oppose that in load winding 52. so that the coil 53 leg of core 65 will become saturated during the second half cycle of the source 48. As a result, current will flow in the coil 53 to provide a gate signal to controlled rectifier 50 which then becomes conductive to provide a second voltage impulse to the coil 47 which is opposite in polarity to that of first voltage pulse. In this manner, voltage pulses of alternating polarity will be supplied to the coil 47 during each alternate half cycle of the source 48.

Neglecting for the moment the effect of the feedback coil 55, the firing angle or point in each half cycle at which each of the controlled rectifiers 49 and 50 become conductive, is determined by the magnetic properties of the magnetic amplifier 51 and the voltage magnitudes of the alternating source 48 and that applied across the control coil 54 and this, in turn, determines the size of the alternating voltage pulses supplied to the coil 47.

Assume that during the initial half cycle of the alternating voltage pulses just discussed, the legs of the electromagnetic 45 have the polarity indicated in FIG. 2. This will cause the poles of the permanent magnet 44 to be attracted by the unlike poles of the electromagnet 45 and repelled by the like poles thereof to cause a net leftward force on the permanent magnet 44, the armature 43, the mass 40 and the tray 34. During the next half cycle of the alternating voltage pulses, the polarity of the legs of electromagnet 45 will reverse so that the permanent magnet will be attracted and repelled toward the right as seen in FIG. 2. Thus, with each reversal of polarity, the magnetic forces acting on permanent magnet 44 are reversed to move the armature 43, the mass 40 and the tray 34 in the opposite direction. Also, when the tray is in the extreme position in either direction, the springs 41 will be extended so that they will aid in the return movement in the opposite direction. In this manner, the tray 34 is made to vibrate uniformly and cause the flow of material 66 from the storage bin 31, down the tray 34 and off its lower end.

It has been found, that within certain limits, the amplitude of vibration of the vibratory feeder 30' is proportional to the weight of material 66 disposed on the tray 34, as indicated in FIG. 3. It has also been found that the amount of material fed in 'feet per minute is also proportional to the weight of the material on the tray 34 as indicated in FIG. 4. For this reason, the amplitude of vibrations of the tray 34 is an accurate indication of the quantity of material being discharged. It has also been found that because the amplitude of the vibrations of tray 34 increases with increased voltage on coil 47, the material discharged increases as the voltage applied to the coil 47 increases, as indicated in FIG. 5.

These factors are applied in controlling the weight of the material discharged from the tray 34 by controlling the voltage applied to the coil 47 in response to the amplitude of vibration in the tray 34. Thus, the feedback transducer 37 senses the amplitude of the tray 34 vibrations and provides a voltage signal functionally related thereto. This voltage signal is applied to the control mechanism 38 which correspondingly modifies the voltage output of the supply circuit 36.

More specifically, the permanent magnet 59 of the feedback transducer 37 vibrates with the tray 34 to induce a voltage in the fixed coil 60 which is proportional to the amplitude of these vibrations. This voltage signal is rectified and applied across the potentiometer 62 to which the feedback coil 55 is connected. Because the coil 55 is wound so that the flux resulting from the voltage thereacross will be in opposition to the flux produced by the coil 54, the vibration amplitude related voltage across the coil 55 will tend to increase the firing angles of each of the controlled rectifiers 49 and 50. This, in turn, reduces the size of the voltage impulses provided to the coil 47. In this manner, the RMS value of voltage applied to the coil 47 and, hence, the amplitude of vibrations of the tray 34 will be a function of the difference between the voltages applied to the control coil 54 and the feedback coil 55.

For example, should the amplitude of vibrations of the tray 34 produce a feed rate of material 66 which is below the desired value, the output of the transducer 37 will correspondingly decrease. This, in turn, will decrease the voltage across feedback coil 55 to decrease the firing angles of each of the control rectifiers 49 and 50 so that the RMS value of voltage applied to coil 47 will increase. This increases the amplitude of the vibrations of the tray 34, which in turn, increases the feed rate therefrom. As the amplitude of vibration of tray 34 increases to the desired value, the output of the feedback transducer 37 will increase to increase the voltage applied to the feedback coil 55. This, in turn, increases the firing angles of controlled rectifiers 49 and 50 so that the voltage applied to coil 47 Will decrease until an equilibrium condition is reached.

Conversely, if the feed rate from the tray 34 should become too large, the amplitude of vibrations will also have increased from the desired value to cause an increase in the output from the feedback transducer 37. This increases the voltage across the feedback coil 55 to increase firing angles of the controlled rectifiers 49 and 50 to decrease the RMS value of voltage applied to the coil 47 of the electro'magnet 45. As a result, the amplitude of the vibration of the tray 34 are decreased and the system is again brought to equilibrium.

According to one example of how the vibratory feeder 30 may be operated with the vacuum degassing apparatus 10, the storage bin 31 is first filled with the material 66 and then the hopper 25 and the casings 29 and 29' enclosing the \u'bratory feeder 30 and the storage bin 31, are sealed. The furnace in which the molten metal 12 is being melted is then tapped and the molten metal is poured into the ladle 11. The weight of metal in ladle 11 is determined and the ladle is then transferred from the furnace to the vacuum degassing apparatus 10. The vacuum degassing apparatus 10 is then lowered so that the lower end of pipe 18 is immersed beneath the level of the molten metal 12 and a vacuum is drawn through the pipe 20 to draw the molten metal 12 into the chamber 17. After a few cycles of the vacuum degassing apparatus wherein the melt 12. in the ladle 11 is intermixed, a chemical analysis of the material may be taken. The weight of material necessary for the amount and chemical analysis of the metal in the ladle 11 is then determined and the timer 53 set so that this exact quantity of material will be fed whereupon the feeding of material may commence. The material 66 is then fed for the requisite period of time as the metal 12' is being degassed. If it is desired to repeat the degassing operation, the degassing vessel 10 is raised to discharge the molten metal 12 from the chamber 17 and then again lowered to draw second quantity of molten metal 12' into said chamber. If desired, a second quantity of material 66 may also be fed into the chamber 17 during the second or any subsequent degassing cycle.

In this manner, the correct quantity of material 66 may be fed into a succession of ladles being degassed without opening the hopper 25 or the casings 29 and 29' and even through the weight and chemical composition of the succeeding ladles may vary considerably.

The adjustable resistor 56 performs the function of a1- lowing the system to be calibrated in relation to the weight and density of the material being fed. Thus, the correct feed rate can be achieved if the system is employed at different times to feed the different materials.

It will be appreciated that because any minor variations in the voltage of the source 48 will tend to modify the feed rate, such variations will be sensed by the feedback transducer 37 which will modify the firing angles of the controlled rectifiers 49 and 50 in the manner tending to correct for such variations. As a result, the feed rate will be held substantially constant regardless of minor variationsin the voltage of the alternating supply 48.

Another factor tending to modify the feed rate from the tray 34- is the weight of material in the storage bin 31 which tends to increase the weight on the tray 34 and thereby increase the amplitude of vibrations in the tray 34. Thus, when the bin 31 is full, the higher weight is sensed by the feedback transducer 37 which increases the voltage applied to the coil 55 which, in turn, increases the firing angle of each of the controlled rectifiers 49 and 50 so that the voltage applied to the coil 47 is likewise reduced. As a result the amplitude of vibrations will be decreased so that the material will be fed from the tray 34 at the desired feed rate. As the material 66 in the storage bin 31 gradually discharges into the tray 34 this weight of material on tray 34 will decrease tending to decrease the amplitude of vibrations thereof. This decrease will also be sensed by the feedback transducer 37 which decreases the voltage across feedback coil 55 to decrease the firing angles of each of the controlled rectifiers 49 and 50 so that the voltage applied to the coil 47 will increase as the weight of material of the bin 66 decreases. As a result the feed rate remains substantially constant regardless of the gradual decrease of material in the storage bin 31.

While the invention has been discussed with regard to a feedback transducer which measures the amplitudes of the vibration of the tray 34, it has also been found that the frequency of vibration is also an indication of the material feed rate, as illustrated in FIG. 6. Accordingly, a feedback transducer which produces an electrical signal functionally related to the vibratory frequency can also be employed. Also, while the invention has been described in relation to a particular type of vacuum degassing apparatus, those skilled in the art will appreciate that it has application to other types of vacuum apparatus as well.

In addition, while only a single embodiment of instant invention has been shown and described, it is not intended to be limited thereby but only by the scope of the appended claims.

We claim:

1. In a material feeding mechanism, the combination of material feeding means and storage means disposed adjacent said feeding means and having discharge means communicating with said feeding means wherein at least a portion of the weight of the material in said storage means bears on said feeding means, electroresponsive vibration producing means coupled to said material feeding means for producing vibrations therein having amplitude and frequency magnitudes functionally related to an applied electrical quantity and the weight of material on said feeding means for discharging material therefrom at a rate functionally related to said magnitudes, first means coupled to said material feeding means for producing a first electrical signal functionally related to one of said magnitudes, means for producing a reference electrical signal, adjustable energizing circuit means coupled to said vibration producing means for providing said electrical quantity thereto, and second means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting said electrical quantity in accordance with the difference between said first electrical signal and said reference signal to maintain a substantially constant material feed rate as the weight of material on said feeding means decreases.

2. In a material feeding mechanism, the combination of material feeding means and storage means disposed adjacent said feeding means and having discharge means communicating with said feeding means wherein at least a portion of the weight of the material in said storage means bears on said feeding means, electroresponsive vibration producing means coupled to said material feeding means for producing vibrations therein having an amplitude functionally related to an applied electrical quantity and the weight of material on said feeding means for discharging material therefrom at a rate functionally related to said amplitude, first means coupled to said material feeding means for producing a first electrical signal functionally related to said amplitude, means for producing a reference electrical signal, adjustable energizing circuit means coupled to said vibration producing means for providing said electrical quantity thereto, and second means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting said electrical quantity in accordance with the difference between said first electrical signal and said reference signal so that a substantially constant feed rate is maintained as the weight of material on said feeding means decreases.

3. In a material feeding mechanism, the combination of resiliently mounted material feeding means and storage means disposed adjacent said feeding means and having discharge means communicating with said feeding means wherein at least a portion of the weight of material in said storage means bears on said feeding means, electrorespon sive vibration producing means coupled to said material feeding means for vibrating the same at an amplitude functionally related to an applied electrical quantity and the weight of material on said material feeding means, feedback transducer means coupled to said material feeding means for producing an electrical signal functionally related to the amplitude of the vibration of said material feeding means, means for producing a reference electrical signal, adjustable energizing circuit means coupled to said vibration producing means for providing said electrical quantity thereto, control means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting said electrical quantity in accordance with the difference between said reference signal and said vibration amplitude related signal so that a substantially constant feed rate is maintained as the weight of material on said feeding means decreases, and timer means operable to maintain the energization of said vibration producing means by said energizing circuit means for a predetermined period.

4. In a vacuum degassing apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including variable output material feeding means, and storage means disposed adjacent said feeding means and having a discharge opening therein communicating with said feeding means wherein at least a portion of the weight of the material in said storage means bears on said feeding means, electroresponsive means coupled to said material feeding means for actuating the same to produce a material feed rate functionally related to the magnitude of an applied electrical quantity and the weight of material on said feeding means, first means coupled to said material feeding means for producing a first electrical signal functionally related to said material feed rate, second means for producing a reference electrical signal, adjustable energizing circuit means coupled to said material feeding means for applying an electrical quantity thereto, third means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting the magnitude of said applied electrical quantity in acc0rdance with the difference between said first voltage signal and said reference electrical signal so that a substantially constant material feed rate is maintained as the weight of material on said feeding means decreases, and timer means operable to maintain the energization of said electroresponsive means by said energizing circuit means for a predetermined period.

5. In vacuum degassing apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including resiliently mounted material feeding means and storage means disposed adjacent said feeding means and having discharge means communicating with said feeding means wherein at least a portion of the weight of material in said storage means bears on said feeding means, electroresponsive vibration producing means coupled to said material feeding means for producing vibrations therein having amplitude and frequency magnitudes functionally related to the magnitude of an applied electrical quantity and the weight of material on said feeding means, first means coupled to said material feeding means for producing a first electrical signal functionally related to one of said magnitudes, second means for producing a reference electrical signal, adjustable energizing circuit means coupled to said vibrations producing means for providing said electrical quantity thereto, third means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting the magnitude of said applied electrical quantity in accordance with the difference between said first electrical signal and said reference electrical signal so that a substantially constant feed rate is maintained as the weight of material on said feeding means decreases, and timer means operable to couple said vibrations producing means to said energizing circuit means for a predetermined period.

6. In vacuum degassing apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including material feeding means and storage means disposed adjacent said feeding means and having a discharge opening communicating with said feeding means wherein at least a portion of the weight of material in said storage means bears on said feeding means, electroresponsive vibration producing means coupled to said material feeding means for vibrating the same at an amplitude functionally related to the magnitude of an applied voltage and to the weight of material on said material feeding means, feedback transducer means coupled to said material feeding means for producing a first electrical signal functionally related to the amplitude of the vibrations of said material feeding means, adjustable energizing circuit means coupled to said vibration producing means for providing voltage thereto, and control means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting the amplitude of said applied voltage in accordance with the difference between said reference electrical signal and said vibration amplitude related electrcal signal so that a substantially constant material feed rate is maintained as the weight of material on said feeding means decreases.

7. In vacuum degassing apparatus, the combination of a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including resiliently mounted material feeding means and storage means disposed above said feeding means and having a discharge opening communicating with said feeding means wherein at least a portion of the weight of material in said storage means bears on said feeding means, electroresponsive vibration producing means coupled to said material feeding means for vibrating the same at an amplitude functionally related to an applied voltage and to the weight of material on said material feeding means, feedback transducer means coupled to said material feeding means for producing a voltage signal functionally related to the amplitude of the vibrations of said material feeding means, means for producing a reference voltage signal, adjustable energizing circuit means coupled to said vibration producing means for providing voltage thereto, control means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting said applied voltage in accordance with the difference between said reference voltage signal and said vibration amplitude related voltage signal so that a substantially constant material feed rate is maintained as the weight of material on said feeding means decreases, and timer means coupled to said reference voltage signal means and operable to maintain the energization of said vibration producing means by said energizing circuit means for a predetermined period.

8. In vacuum idegrassin'g apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including resiliently mounted tray means, vibration producing means including electromagnetic means having a coil and core and permanent magnetic means disposed adjacent said core, one of said magnetic means being coupled to said material feeding means for vibrating the same to .produce a material feed rate functionally related to the alternating electrical energy applied to said coil and the weight of material on said tray means, first means coupled to said material feeding means for producing a first electrical signal functionally related to said material feed rate, means for producing a reference electrical signal, adjustable energizing circuit means coupled to said coil for supplying alternating electrical energy thereto, second means coupled to receive said electrical signals and coupled to said energizing circuit means for adjusting the electrical energy supplied thereto in accordance with the difference between said first voltage signal and said reference electrical signal so that a substantially constant feed rate is maintained as the weight of material on said tray means decreases, and timer means operable to maintain said coil energized by said energizing circuit means for a predetermined period.

9. In vacuum degassing apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including resilently mounted tray means and storage means disposed above said tray means, said storage means having a dicharge opening above said tray means wherein at least a portion of the weight of material in said storage means bears on said tray means, vibration producing means including electromagnetic means having a coil and a core and permanent magnetic means disposed adjacent said core, one of said magnetic means being coupled to said tray means for producing vibrations therein having amplitude and frequency magnitudes functionally related to the alternating voltage applied to said coil and to the weight of material on said tray means, feedback transducer means coupled to said material feeding means for producing a first voltage signal functionally related to one of said magnitudes, means for producing a reference voltage signal, adjustable energizing circuit means coupled to said coil for applying an alternating voltage thereto, control means coupled to receive said voltage signals and coupled to said energizing circuit means for adjusting said applied voltage in accordance with the difference between said reference voltage signal and said first voltage signal so that a substantially constant feed rate is maintained as the weight of material on said tray means decreases.

10. In vacuum degassing apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including resiliently mounted inclined tray means and storage means having discharge opening means disposed above said tray means wherein at least a portion of the weight of material in said storage means bears on said tray means, vibration producing means including electromagnetic means having a coil and a core and permanent magnetic means disposed adjacent said core, one of said magnetic means being coupled to said tray means for vibrating the same at an amplitude functionally related to the magnitude of an alternating voltage applied to said coil and to the weight of material on said tray means, feedback transducer means coupled to said material feeding means for producing a voltage signal functionally related to the amplitude of vibration of said tray means, means for producing a reference voltage signal, adjustable energizing circuit means coupled to said coil for applying an alternating voltage thereto, control means coupled to receive said voltage signals and coupled to said energizing circuit means for adjusting said applied voltage in accordance with the difference between said reference voltage signal and said vibration amplitude related voltage signal so that a substantially constant feed rate is main tained as the weight of material on said tray means decreases, and timer means coupled to said reference voltage signal means and operable to maintain said coil energized by said applied voltage for a predetermined period.

11. In vacuum degassing apparatus, the combination of, a vacuum chamber having at least one molten metal conducting pipe opening into its lower end, a sealed feeding assembly opening into said vacuum chamber and including resiliently mounted inclined tray means and storage means having a discharge opening above said tray means wherein at least a portion of the weight of material in said storage means bears on said tray means, vibration producing means including electromagnetic means having a coil and a core and permanent magnetic means disposed adjacent said core, one of said magnetic means being coupled to said tray means for vibrating the same at an amplitude functionally related to the magnitude of an alternating voltage applied to said coil and to the weight of material on said tray means, feedback transducer means coupled to said material feeding means for producing a voltage signal functionally related to the amplitude of vibration of said tray means, means for producing a reference voltage signal, energizing circuit means coupled to said coil for applying an alternating voltage thereto, electronic switching circuit means connected between said source and said coil, magnetic amplifier means having control winding means coupled to receive said voltage signals and load windings coupled to said switching circuit means for adjusting the firing angles thereof in accordance with the difference between said reference voltage signal and said vibration amplitude related voltage signal so that a substantially constant feed rate is maintained as the weight of material on said tray means decreases, and timer means coupled to said reference voltage means and operable to maintain said coil energized by said applied voltage for a predetermined period.

12. In material feeding mechanism, the combination of resiliently mounted inclined tray means and storage means having a discharge opening above said tray means wherein at least a portion of the weight of material in said storage means bears on said tray means, electroresponsive vibration producing means coupled to said tray means for vibrating the same at an amplitude functionally related to the magnitude of an alternating voltage applied thereto and to the weight of material on said tray means, feedback transducer means coupled to said material feeding means for producing a voltage signal functionally related to the amplitude of vibration of said tray means, means for producing a reference voltage signal, energizing circuit means coupled to said coil for applying an alternating voltage thereto, electronic switching circuit means connected between said source and said vibration producing means, magnetic amplifier means having control winding means coupled to receive said voltage signals and load windings coupled to said switching circuit means for adjusting the firing angles thereof in accordance with the difference between said reference voltage signal and said vibration amplitude related voltage signal so that the material feed rate will be maintained constant as the weight of material on said tray means decreases, and timer means coupled to said reference voltage means and operable to maintain said coil energized by said applied voltage for a predetermined period.

References Cited UNITED STATES PATENTS 2,402,183 6/1946 Rowe et al 198-37 XR 2,609,965 9/1952 Kast 222- 2,618,406 11/1952 Kast Q 222-55 2,832,462 4/1958 Simer 19837 2,872,180 2/ 1959 Tietig. 2,921,712 1/1960 Dickerson 22255 2,969,893 1/1961 Peeters 22255 XR 3,027,150 3/1962 Harders. 3,154,404 10/ 1964 Lorenz. 3,203,686 8/1965 Wooding et al. 3,321,300 5/1967 Worner.

FOREIGN PATENTS 796,369 6/1958 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner. S. AWNEAR, Assistant Examiner. 

